Pneumatic false twist interlaced yarn

ABSTRACT

Apparatus for interlacing a filament yarn to give it compactness and other characteristics of a twisted yarn comprising a pair of spaced oppositely functioning pneumatic false twisters with the downstream twister having a smaller yarn passage than the upstream twister.

United States Patent 1191 Lloyd et al.

[ PNEUMATIC FALSE TWIST INTERLACED YARN [75] Inventors: Neil E. Lloyd; Walter B. Mather,

III, both of Rock Hill, SC.

[73] Assignee: Celanese Corporation, New York,

[22] Filed: Nov. 2, 1971 [21] Appl. No.: 194,850

Related U.S. Application Data [62] Division of Ser. No. 42,404, June l, 1970, Pat. No.

[52] U.S. Cl 57/140 R [51] Int. Cl D02g 3/24 [58] Field of Search 57/34 B, 140 R, 140 BY,

[ Sept. 24, 1974 [56] References Cited UNITED STATES PATENTS 3,l 10,151 11/1963 Bunting, Jr. et al 57/157 F FOREIGN PATENTS OR APPLICATIONS 6,912,566 2/1970 Netherlands 57/34 B Primary Examiner-John Petrakes Attorney, Agent, or Firm-Thomas J. Morgan; Robert J. Blanke [57] ABSTRACT Apparatus for interlacing a filament yarn to give it compactness and other characteristics of a twisted yarn comprising a pair of spaced oppositely functioning pneumatic false twisters with the downstream twister having a smaller yarn passage than the upstream twister.

6 Claims, 5 Drawing Figures PNEUMATIC FALSE TWIST INTERLACED YARN BACKGROUND OF THE INVENTION The present invention, which is a divisional application of application Ser. No. 42,404 filed June 1, 1970, now US. Pat. No. 3,775,958, relates to a novel apparatus and process for interlacing the filaments of a multifilament yarn so as to impart thereto the characteristics of a yarn which has twist.

In the production of continuous filament yarns they are usually collected either with a ring and traveller takeup or with a horizontal zero twist takeup. The ring and traveller imparts a small amount of twist, the exact magnitude depending upon the rotational speed of the collector and the running speed of the yarn. While either the low twist, e.g., about 0.25 turns per inch, or the zero twist yarns are suitable directly for certain end uses, for most knitting and weaving purposes the yarns are not suitable for use as is. The high speeds encountered in processing frequently make the filaments balloon out and separate from the main bundle with subsequent breakage due to snagging upon the supply package from which it is withdrawn or from contact with yarn guiding surfaces over which it is drawn. To prevent this possibility, and for other reasons as well, it is customary to twist the yarn whereby the tendency of individual filaments to splay out and/or break is minimized. Moreover, even if an individual filament should break it will be held in its own bundle, rather than snarling the nearby yarns.

To put 3 or more turns per inch into a yarn is relatively time consuming, i.e. the maximum linear speed of the yarn will be only a few hundred meters per minute. Accordingly, if such twisting were done on the yarn as first taken up after extrusion, it would limit the extrusion speed. Consequently, it is the practice to extrude and collect the yarn and then to transfer the yarn to another machine where it is twisted, this obviously entailing additional equipment and manual labor.

Techniques have therefore evolved to eliminate twisting, i.e. to perform its compacting function in some other manner at speeds high enough not to slow down extrusion. One such technique is to glue the filaments together lightly at spaced locations as by applying yarn size. Another technique for folding filaments into the body of the yarn to maintain a compact bundle is described in US. Pat. No. 2,673,442 which describes subjecting the yarn to two sequential false twisting devices operating in opposite senses, the false twisting devices being skew guides, rotating twisters, helical groove guide members or fluid jets. In putting these suggestions into practice, abandoned US. application Ser. No. 563,234 discloses use of two spaced oppositely directed pneumatic false twisters operating on the running yarn.

It is an object of the present invention to provide a new process and apparatus for achieving levels of compaction with pneumatic false twisters higher than heretofore attainable. Other objects and advantages of the invention will become apparent from the following detailed description in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of the apparatus in accordance with the invention;

FIG. 2 is a perspective view of the slub catcher or oscillating damping guide of FIG. 1;

FIG. 3 is a transverse vertical section through one of the jets of FIG. 1;

FIG. 4 is an enlargement of a portion of FIG. 3; and

FIG. 5 is a perspective view of the jets and air supply of FIG. 1.

In accordance with the invention, it has been found that the desired effect of higher compaction levels can be achieved if the two pneumatic false twisters are of different dimensions from one another. Specifically, if both are supplied with the same pressurized fluid, e.g. the same compressed air, it has been found advantageous to make the cross-sectional area of the yarn passage of the downstream twister smaller than that of the upstream twister. The yarn passages are generally circular in cross-section and the area of the upstream passage is about to 300% that of the downstream passage and preferably about 200 to 250%.

The particular apparatus sets up complex forms of wave motions in the running yarn between the oppositely acting false twisters as well as upstream and downstream thereof and in accordance with a further aspect of the invention a damping guide is included to limit oscillation in the running end of yarn upstream of the apparatus, further increasing the compaction level.

Referring now 'more particularly to the drawings, in FIG. 1 there is shown a multifilament yarn 12 running from a source (not shown) which may be an extrusion cabinet or a package, the yarn making a 20 wrap, as indicated, around a circular pin 14, then passing through the slot of a damping guide 16 describedmore fully hereinafter. The yarn next passes through a passage in upstream pneumatic false twister l8, thence through a passage in downstream pneumatic false twister 20. In this embodiment twisters l8 and 20 are integral and share a common base 22 through which air is supplied as shown more clearly in FIGS. 3 and 5. The yarn 12 after leaving the downstream twister 20 passes to a guide 24 which is the balloon guide of a conventional ring and traveller takeup for collecting yarn on a bobbin 26 carried on a rotating spindle 28.

The damping guide 16 is of the type conventionally known as a slub-catcher. It comprises a flat plate 30 carrying a pair of wear-resistant inserts 32, 34 defining therebetween a narrow slot of precise dimension. In the event of an enlargement in the yarn, i.e. a slub, it will be caught by the inserts 32, 34 and prevented from advancing. In the instant apparatus the guide 16 serves to confine the oscillations created in the yarn to the pneumatic false twisting zone thereby intensifying the compaction action.

In FIG. 3 there is shown a section through the up stream false twister 18, approximately to scale. In the block of metal making up twister 18 there is a notch 36 communicating with a slot 38 through which a yarn may be introduced or strung up into yarn passage 40. The yarn passage 40 runs the length of twister l8 and approximately halfway along its length it is intersected near its top by an air passageway 42 preferably of circular cross-section for ease of formation. Passageway 42 communicates with a further passageway 44 in base 22 through which compressed air is supplied by a coupling 46 (FIG. 5) to both twisters l8 and 20.

As can be seen in FIG. 4, the air passageway 42 is essentially tangential to the yarn passage 40 so that compressed air leaving passageway 42 will swirl around the periphery of passage 40 and create a vortex. Filaments of the yarn l2 caught in the swirling air stream will tend to be twisted and the non-uniform action across the filament bundle will result in the desired compaction, in cooperation with the other twister 20, i.e. by itself twister 18 would put false twist into the yarn. By false twist is meant temporary twist; thus the yarn has twist while it is under the influence of the twister but some distance downstream of the nozzle this twist will have been lost and the yarn restored to its initial twist level, in this case zero twist.

The compressed air passageway 42 is preferably canted or tilted slightly off tangential to provide a more smoothly swirling stream and also to provide an air block which prevents accidentally blowing the yarn 12 out string up slot 38.

The twister 20 is generally identical in structure with twister 18 with the exceptions that the swirling air stream is of opposite sense and the yarn passage 48 is smaller in cross-sectional area than passage 40. Thus, whereas air passageway 42 enters from the right in FIG. 4 to create a counter-clockwise vortex in twister 18, in twister 20 the air passageway entry to the bore would be at the left to create a clockwise vortex.

Somewhere between the twisters 18 and 20 the yarn 12 is under the influence of twisting forces from both twisters. Without wishing to be bound thereby it is believed a helical wave configuration is imparted to the yarn in the upstream twister, the diameter of the helix being the diameter of the yarn passageway. A similar effect is produced in the second yarn passageway, except that the helix is now smaller in diameter. This greater intensity affects the location of the zone of twist reversal which is at some point between the two twisters, the decrease in the downstream diameter tending to move such point upstream. The complex wave motions, which are mechanical in character, interact and cause the filaments in the yarn individually or as subbundles to be displaced relative to neighboring filaments and sub-bundles to effect the compaction. This is to be distinguished from a false twisting of the entire bundle where there would be no interlacing and compaction.

Regardless of the theory, however, higher levels of compaction have been achieved using the instant system. Yarns upon which the invention can operate include all multifilament yarns of polymers such as cellulosics, e.g. cellulose acetate and triacetate and rayon, nylons such as polyhexamethylene adipamide, polycaprolactam and polymers of other dicarboxylic acids and diamines or aminocarboxylic acids, polyesters such as polyethylene terephthalate and polymers of one or more other dicarboxylic acids and glycols, vinylidene polymers such as olefins. e.g. polyethylene and polypropylene, vinyl chloride and/or vinylidene chloride, acrylonitrile, and the like. Even silk or glass or metal filament yarns may be so processed. In addition, filaments of different chemical composition can be worked upon simultaneously and they will be interlaced and effectively blended at the same time. If desired, stable fiber yarn may be processed simultaneously with a continuous filament yarn and some of the staple fibers will be locked in the final structure.

The denier of the individual filaments may be as high as 50 or more or as low as 0.5 denier or less. The tension on the yarn in grams per denier may have to be lowered and the air pressure may have to be adjusted upwardly to permit interlacing of heavy denier filaments and opposite adjustment should be made for very low denier filaments. The pressure of the air used may range from as low as about 20 psig up to about 100 or more but for ease of achievement with inexpensive equipment, for safety and practicality the pressure desirably ranges from about 40 to 80 and preferably about 60 to psig.

The pressure in each twister may be different but is preferably the same, using a single common supply. The preferred pressurized fluid is air but steam, nitrogen, carbon dioxide, and the like, may be used. The temperature is dependent solely on the physical properties of the yarn and convenience, with ambient temperature therefore being preferred.

The tension on the running yarn, measured upstream of the jets, may be as low as 0.005 gram per denier and may be so high as to approach the breaking point of the filaments. Higher tensions, however, increase the chance of breaking filaments which are weaker than normal, and they make it necessary to increase the air pressure to obtain a given degree of interlacing and compaction. Consequently, the tension is desirably kept below about 0.5 gram per denier and usually below about 0.1 gram per denier. It should be at least about 001 gram per denier and usually at least about 0.02 gram per denier to prevent the yarn from bulking under the influence of the air, i.e. forming loops, or being blown out the string up slot. The tension may be adjusted by controlling the weight of the traveler when using a ring and traveler takeup.

The total denier of the yarn being subjected to the dual opposed false twisting may be several thousand denier, e.g. 4,000 or more, although generally it is below 1500 and desirably it ranges from about 20 to 200 preferably about 40 to 150. For best results there should be at least about 5 filaments, desirably at least about 8 and preferably at least about 10. The yarn being tested is generally without twist initially, although it may be collected with twist superimposed if desired, or it may be separately aftertwisted. The handling characteristics, however, will be equivalent to a yarn having a much higher level of real twist. Alternatively, the yarn may be collected without twist. Possibly the starting yarn may have some twist, e.g. 0.] turn per inch or possibly as much as 1 turn per inch or even more. Should the yarn have such twist preferably the vortex of the first pneumatic false twister will be of opposite sense so as to open the yarn, i.e. if the yarn has a clockwise twist the first twister of the pair should have its air passageway so directed as to create a counterclockwise vortex. Otherwise, it is without moment which twister is first encountered.

The length of the yarn passage through each of the pneumatic twisting jets may range from about 0.3 to 4.00 inches, preferably from about 0.5 to 1.00 inches. To some extent the length is determined by the speed at which it is intended to run the system i.e. the length should be so chosen that the yarn will be subjected to the action of each vortex for about 0.0003 to 0.2 and preferably about 0.0005 to 0.003 seconds. Shorter times will result in the yarn not having been exposed to the action long enough to achieve the desired result, although this could be compensated to some extent by increasing the pressure. Longer exposure times are without detriment but increase the cost of the apparatus and require more room to accommodate the lengthened structure.

The spacing between the two twisters may also be varied and generally ranges from about 0.1 to 24 and preferably 0.5 to 1.5 inches. Outside of these ranges it is found that the degree of compaction tends to diminish somewhat. The cross-sectional area of each bore may vary within relatively wide limits and will, of course, be large enough to permit a vortex to be created and to accommodate the running yarn as well. When operating with textile deniers, e.g. 150 denier or less, the cross-sectional area occupied by the yarn is so small that it can be ignored. The cross-sectional area of the smaller downstream bore may range from about 0.001 to 0.015 and preferably 0.002 to 0.01 sq. in. The upstream bore will have an area ranging from about 150 to 300% that of the downstream bore and preferably about 200 to 250%. It has been found that operating within these ranges tends to produce the highest degree of compaction in a given system, in contrast with using either bores of equal cross-sectional areas or positioning the bore of larger cross-sectional area downstream.

The air passageway may be slightly off tangential as shown in FIG. 4 or it may be perfectly tangential i.e. the uppermost portion of the passageway being tangential to the circumference of the circular yarn passage. If the axis or the lower edge of the air passageway is tangential to the yarn passage, some measure or turbulence will result because the air will not be smoothly deflected into a rotating stream or vortex. While the air passageway is shown in FIG. 4 as adjacent the yarn string up slot, it could of course be displaced 90 or more degrees about the circumference of the yarn passage or, it is even possible to operate without a string up slot, in which case it will be necessary to thread the yarn through the passage with a needle each time there is a yarn discontinuity. The size and the cross-sectional area of the air passageway should be as small as practical to minimize the consumption of pressurized fluid; in practice, diameter ranges from about 0.010 to 0.050 inches and preferably 0.018 to 0.024 inches have been found suitable for both the upstream and downstream twisters. As seen in plan, the air passageway will intercept the yarn passage approximately midway along the latters length and the air passageway may be perpendicular to the yarn passage or it may be directed at any angle relative thereto, decreasing the tension on the yarn if forwardly directed and increasing the yarn tension if rearwardly directed. The air passageway may define an angle of about 75 to about 85 and preferably about 80 with the yarn passage and directs air forwardly.

The slub catcher or damping guide shown in FIG. 2 will have a slot whose dimension is dependent upon the diameter of the yarn bundle i.e. its denier. The width of the slot should be about 40 to 150% and preferably 50 to 100% the diameter of the bundle to be effective. With 55 and 75 denier yarns a slot width of about 0.0030.008 inch and especially 0.004 inch has been found quite satisfactory. In addition to catching enlargements in the yarn, the guide serves to dampen oscillation in the yarn being subjected to the pneumatic false twisting action. For maximum effect i.e. the highest degree of compaction, it has been found that the guide should be positioned about 0.1 to 1.5 and preferably 0.25 to 1 inch upstream of the upstream jet. While a similar guide maybe positioned downstream of the downstream jet it does not have the same effect on increasing compaction relative to the general system without such guides. The slub catcher eliminates the formation of small loops which otherwise are sometimes found on the first portion of yarn wound on a new bobbin. Its presence also permits use of a lower weight traveler and thus of less tension on the yarn, with attendant increase in compaction. The damping function may be performed with a flat guide over which the yarn runs and makes a sharp angle, thereby limiting oscillation. One may position a further guide downstream of the downstream jet properly to define the yarn path through the jets. The downstream guide may be of similar form and its location is not critical. Desirably, however, this downstream guide may be the balloon guide of a conventional ring and traveler takeup, which guide is about 0.375 'to 1.5 and preferably 0.62 to 1.00 inch downstream of the downstream jet.

Reference has been made heretofore to the degree of compaction which refers to the extent of interlacing between the filaments. In a twisted yarn, the greater the twist the more compact will be the bundle, i.e. all filaments will be held tightly together and none will stray from the bundle. In interlaced yarn such as produced in accordance with the present information which yarns generally have no twist, the degree of compaction is determined as follows:

A pin is put through a yarn sample (pretensioned to a value equal to 0.2 times the denier of the yarn expressed in grams) and is pulled longitudinally through the yarn until, as a result of encountering interlacings and cross-overs amongst filaments, the incremental force required to advance the pin further exceeds denier per filament as grams tension. The distance in centimeters which the pin has moved is measured and the average of 20 such measurements is used as an index of the degree of compaction. (It will then be understood that lower needle pull values represent the higher levels of compaction.) Since the compaction may vary from inside to outside of each bobbin, the measurements should take this into consideration and should include beginning, middle and end run samples. The measurement of compaction may also be accomplished semi-automatically in accordance with the teachings of copending and commonly assigned application Ser. No. 812,219 filed Apr. 1, 1969, by Bulla et al.

The invention will be further described in the following illustrative examples.

EXAMPLE 1 A zero twist cellulose acetate yarn made up of 15 filaments and having a total denier of 55 is processed through the apparatus of FIG. 1 at a speed of about 900 meters per minute. In this run the yarn makes a 0 wrap in contact with pin 14 which has 'a diameter of 0.16 inch and the center line of which is 0.455 inch upstream of twister 18. The yarn passes freely through the 0.004 inch wide slot of oscillation damping guide 16 provided 0.375 inches upstream of jet l8. Jets 18 and 20 are each 0.56 inch long and are spaced apart 0.5 inch. The cross-sectional area of the yarn passage of jet 18 is 0.007 sq. in. and that of jet 20 is 0.003 sq. in., both yarn passages being circular in shape. The air passageway to each yarn passage is circular in shape and has a diameter of 0.021 inch. As viewed from above, air enters each yarn passage at an angle, canted forwardly, at a location mid-way along its length. The pressurized fluid is at a pressure of 60 psig and is discharged at the rate of about 0.5 scfm per jet. The yarn string up slots 38 have a width of 0.005 inch. Threefourths inch downstream of downstream jet 20 the yarn encounters balloon guide 24 from whence it is collected in conventional manner, by ring and traveller takeup, on a. bobbin 26 rotating at a speed of 6500 rpm V with a traveler weighing 0.040 gm. The tension on the running yarn at a point just upstream of pin 14 is measured at 2.5 grams. The degree of compaction of yarn on the bobbin is measured by first discarding several yards of yarn, followed by removal of a sample, backtwisting to remove all the twist imposed by the takeup, i.e. restoring it to zero twist condition, and carrying out the measurements as described hereinabove. The degree of compaction averaged 2.5 cms. as measured by the needle pull test.

EXAMPLE 2 In a manner similar to that described in Example 1, but employing no oscillatory damping guide a series of paired jets spaced by 0.5 inch differing only in the respective cross-sectional areas of the individual jets (each defining a circular yarn treatment bore) were tested for effectiveness in compaction. In each case, air entry ports canted forwardly to the threadline path at an aspiration angle of 80 were employed, and the jets were operated at 60 psig. The runs were conducted at 3 wrap over the pin, utilizing a 0.065 gram traveler. The reported compaction values represent an average over 12 bobbins.

The results are tabulated hereinbelow:

Ratio of upstream to downstream Threadline Compaction, bore diameter Tension, gms. cms.

EXAMPLE 3 The run of Example 1 was repeated, utilizing a traveler weight of 0.065 grams. Threadline tension averaged about 3 .2 grams, and compaction values averaged 2.9 cm. over 24 bobbins, with individual values ranging between 1.8 and 3.8 cm. In an otherwise identical run without the oscillatory damping guide, threadline tension averaged about 3.6 grams, and compaction values averaged 5.0 cms. over 12 bobbins.

EXAMPLE 4 age compaction is 2.5 cm.

EXAMPLE 5 A 55/15 zero twist cellulose triacetate yarn and a 20/7 zero twist nylon 66 yarn are passed simultaneously through an apparatus as used in Example 1 with the following changes: The speed is 750 meters per minute. The jets are spaced apart 0.5 inch. The traveler weight is 0.032 gram and the tension on the yarn averages 3.0 grams. The compactness of the well plied yarn is about 2.5 cm.

In the foregoing examples the desired result is achieved with little or no reduction in the physical properties of the yarn. Similarly, the jets undergo little if any wear although preferably the yarn passages are provided in removable, replaceable inserts made of special wear resistant materials.

The yarn is preferably subjected to the instant treatment after extrusion and prior to its initial collection altlfoiighif 1553mm; Been'eom'rsaatfiubjeaea to the treatment in the course of twisting, plying, drawwinding, draw-twisting, beaming, or even weaving or knitting.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the following claims.

Having thus disclosed the invention, what is claimed 1. A continuous filament combination entangled yarn having real twist superimposed thereon, said yarn prior to the addition of said real twist comprising filaments of a cellulose acetate and a nylon wherein the filaments or filament bundles comprising said yarn exhibit a random small degree of residual twist trapped between random periodic points of interaction wherein said filaments or filament bundles are wrapped about the main yarn bundle or. filament bundles, producing a yarn characterize by a needle pull value of less then about 2.0 C and an average spreadability when floated on a water surface, of less than 20 times the normal flat yarn diameter.

2. The continuous filament yarn of claim 1 comprising at least 50 percent by weight of cellulose triacetate, said yarn exhibiting a needle pull value of between about 1.5 and 2.0 cms.

3. The yarn of claim 1, wherein said yarn also exhibits an applied bundle twist of between about 0.2 and 1.0 tpi.

4. The yarn of claim 1, comprising 15 filaments of cellulose triacetate having a total denier of 55 and 7 filaments of nylon having a total denier of 20.

S. The yarn of claim 1, wherein said nylon is hexamethylene diammonium adipate and the nylon filaments comprise up to about 40 percent by weight of the yarn.

6. The yarn of claim 1, wherein said nylon is a poly-v condensate of bis(para-aminocyclohexyl)methane and a dodecandioic acid. 

1. A continuous filament combination entangled yarn having real twist superimposed thereon, said yarn prior to the addition of said real twist comprising filaments of a cellulose acetate and a nylon wherein the filaments or filament bundles comprising said yarn exhibit a random small degree of residual twist trapped between random periodic points of interaction wherein said filaments or filament bundles are wrapped about the main yarn bundle or filament bundles, producing a yarn characterize by a needle pull value of less then about 2.0 C and an average spreadability when floated on a water surface, of less than 20 times the normal flat yarn diameter.
 2. The continuous filament yarn of claim 1 comprising at least 50 percent by weight of cellulose triacetate, said yarn exhibiting a needle pull value of between about 1.5 and 2.0 cms.
 3. The yarn of claim 1, wherein said yarn also exhibits an applied bundle twist of between about 0.2 and 1.0 tpi.
 4. The yarn of claim 1, comprising 15 filaments of cellulose triacetate having a total denier of 55 and 7 filaments of nylon having a total denier of
 20. 5. The yarn of claim 1, wherein said nylon is hexamethylene diammonium adipate and the nylon filaments comprise up to about 40 percent by weight of the yarn.
 6. The yarn of claim 1, wherein said nylon is a polycondensate of bis(para-aminocyclohexyl)methane and a dodecandioic acid. 